1. Field of the Invention
The present invention relates to a shift-operation apparatus for use in an automatic transmission of a vehicle.
2. Description of the Related Art
As apparatus for effecting a shifting operation for an automatic transmission of a vehicle, a shift lever apparatus is generally used which is disposed on a floor surface of the vehicle, is coupled to the automatic transmission, and effects a shifting operation for the automatic transmission mechanically by selecting and operating a lever. In recent years, a shift-operation apparatus has been devised which is disposed in the vicinity of a steering wheel, electrically detects a shift position selected by a shifting operation, and effects a shifting operation for the automatic transmission on the basis of this detected signal.
This type of shift-operation apparatus for an automatic transmission has an operation knob for a shifting operation and a switch for detecting a shift position selected by this operation knob. The shift positions of the operation knob correspond to a P shift range, an R shift range, an N shift range, a D shift range, and the like of the automatic transmission. Each of these shift positions is detected by the switch, and shifts the automatic transmission on the basis of a detected signal.
Among such shift-operation apparatuses for automatic transmissions, there is an apparatus which is arranged to select each shift position by rotating the operation knob with respect to an axis and moving it in the axial direction. For instance, the following shift-operation apparatus is known: Shift positions such as the N shift range, the D shift range, the 2 shift range, and the like are set in correspondence with the rotating direction of the operation knob, and shift positions such as the P shift range, the R shift range, and the like are set in correspondence with the axial direction of the operation knob. As this operation knob is rotated, a shift position such as the N shift range, the D shift range, the 2 shift range, or the like is selected, and as the operation knob is moved in the axial direction, a shift position such as the P shift range, the R shift range, or the like is selected.
With this type of shift-operation apparatus, a displacement of the operation knob in the rotating direction is detected by a switching means such as a contact plate, for instance. Meanwhile, a displacement of the operation knob in the axial direction is detected by another switch or the like as the axial movement of a shaft connected to this operation knob.
However, if such a shift position is further set as is selected by performing both the rotation and axial movement of the operation knob in addition to selecting a shift position in correspondence with the mere rotation and axial movement of the operation knob, there arises a drawback in that the switch for detecting only the axial movement of the operation knob (i.e., the axial movement of the shaft) is unnecessarily actuated when the operation knob is operated to the shift position which is selected by performing both the rotation and axial movement of the operation knob. Accordingly, a countermeasure against this drawback has been required.
Furthermore, in a case where there is provided a mechanism for prohibiting a shifting operation effected by the axial movement of the shaft, i.e., the axial movement of the operation knob (the operation of selecting a shift position such as the P shift range, the R shift range, or the like, as described above) under a predetermined condition (setting the operation knob in a so-called shift-lock state), since the axial movement of the operation knob is prevented, there arises a drawback in that the operation knob cannot be operated to the shift position which is selected by performing both the rotation and axial movement of the operation knob. Hence, a countermeasure against this drawback has also been required.